1) The goals of the Spanish were to build empires both secular and religious. The religious goals were to win people for Catholic church and the secular goals were to gain more power over the southern and northern america to have access to the wealth and gold.
2) The greatest killer was the smallpox diseases that almost erased human life which was spread through direct human contact. Other diseases that killed Native Americans were influenza, malaria, whooping cough, diphtheria, and measles. European also brought in large domestic animals such as sheep, cattle, pig, and horse and plants e.g corn, avocado, squash, pineapple, peanuts, potatoes, etc which was more nutritious than the wheat, rice, barley and oats that the Native Americans were used to consuming.
3) The Europeans claimed their right on claiming the land in America by the authority of the pope. Europeans also claimed to have conquered the native Americans and discovered the land. They claimed possession by occupying the land.